quadraphonic on modern systems (1 Viewer)

[Sathyan]

I've read on the web that you can decode Quadraphonic (from the 70's) LP recordings with Dolby Pro Logic II. Have any of you tried this? Is it true? For those who have/had true Quad systems, how does it compare?

thanks
Sathyan

 

[GregK]

I've heard that QS (RM) encoded matrix quad discs decode moderately well with DPL-2, but SQ does not. With SQ encoded material, information placed in the center rear position will come out of the surrounds accurately, but material placed in left rear or right rear only will come out of all five speakers in DPL-2.

Decent sounding full-logic SQ decoders were hard to come by in quad's hay-day, let alone now. The all-time best SQ decoder was the Tate 101A, which was co-designed by Jim Fosgate. Lately, the 101A can sell up wards to a grand on eBay. Btw: Jim Fosgate designed the Dolby Pro-Logic II decoding system, bringing us full circle. (Pun intended!)

 

[Charles Smith]

Ah, a 12-year-old thread. Perfect!


I've been sorting through my record collection and was surprised to be reminded that I had a few quad discs even though I never had any way to properly listen to them back in the day. I've dug out three so far, representing the SQ, QS, and CD-4 formats -- and there might be a few more to uncover. I think it's the CD-4 one that I cleaned and put on the turntable to see what I'd get. I switched the receiver from stereo to Pro Logic II and got some interesting separation and spread around the room (setup is 7.1), then tried a few other settings like Neo 6 and Neural THX (I don't really know what any of those are).


Results were definitely of interest, even though I have no idea how close to the intended effect they were, or even if I would have gotten that much separation and spread using those settings on a regular stereo LP. I'll have to spend some more time at it.


Anyway, just reading over this and another thread I found here, it appears there is no real equivalent setting for what one was intended to hear with a 1970s quad receiver or decoder. Is that still the case? I should just play around with it and have whatever fun there is to have?

 

[Peter Apruzzese]

If I recall correctly, CD-4 required a special cart and stylus to play in quad. The other two formats SQ and QS (that's not confusing) used a form of matrixing (a little similar to Dolby Surround) to get the back channels.


"I should just play around with it and have whatever fun there is to have?"


Yes, I don't think any modern gear will be completely accurate so just have fun. You might get better results by telling your receiver that you do not have a center speaker (which the quad formats did not use).

 

[Charles Smith]

I was wrong -- the one I tried was SQ, not CD-4.

It just happens that for the CD-4 one, I also have the standard stereo release. Anyway, when I get back to trying these, I'll eliminate the center speaker. Thanks for the reminder on that.

 

[Colin Dunn]

Interesting that this ancient thread has come back to life!


Turns out, it is possible to get faithful reproduction of matrix quad recordings (and preserve them) a couple of different ways.


1) For real-time playback, get a receiver with multi-channel analog input and add the Surround Master SQ Edition (

http://involveaudio.com/product/surround-master/). If you purchase with the SQ option, use SQ for SQ recordings, Involve mode for QS. The Surround Master requires a line-in signal, so you'll want to connect your phono stage to it, then connect the Surround Master to the multi-channel input jacks. This is the best hardware decoder for these old formats that is available today, and is far preferable to using DPL II(x/z) to decode QS.


2) If you lack multi-ch​annel inputs or want to clean up the audio (click / noise reduction), there are computer-based approaches to decoding SQ and QS. Over at the Quadraphonic Quad forums (http://www.quadraphonicquad.com) there are Adobe Audition 3.0 scripts that can be used to take a stereo recording of an SQ or QS quad album, and derive discrete multi-channel audio. Once you have your 4-channel .WAV file, you can play it back on a computer with HDMI digital audio or burn to a DVD-A or Blu-ray audio disc.


For CD-4, you need a demodulator, which outputs a discrete 4-channel line-level signal. These are hard to find in working order these days. If you find one, I suggest recording your CD-4 LPs to 4-track tape or digital immediately so they can be preserved. Much like the computer approach for SQ / QS, you can clean up audio and burn to a modern format and enjoy the surround mix. Recording 4 channels of discrete audio on a computer requires an external multi-channel sound interface, often used in pro audio applications.

 

[Charles Smith]

Thanks! I do have multi-channel inputs and the Surround Master looks like a great item. But now we're talking $500 for my three or four LPs (none of which I'm all that passionate about), so I'm afraid that dog won't hunt. But I'm very glad to know about these two options, believe me, and I'll save the info for possible future reference.

 

[Colin Dunn]

I would agree, $500 is a lot to spend to decode three albums. The Surround Master's Involve mode may also be used for stereo->surround processing.


If you want to go the computer decoding route, you can start for free but I recommend about $140 worth of commercial software - Cirlinca HD-Audio Ultra (for authoring DVD-A / BD) and Click Repair (for cleaning up clicks / pops in vinyl). Technically, Cirlinca is optional if you can play back via HTPC over multi-channel HDMI, but I recommend it for being able to create discs for archival. And then Click Repair is the best reasonably-priced program for cleaning up noise on vinyl. You can test without it if your vinyl is pristine, but if you get into this and start hitting the used record shops to expand your quad vinyl collection, you'll want it.


A high-quality sound interface is strongly recommended, though if you're just testing the process you can use your sound card line-input (beware of noise in a computer though).


Adobe has made Audition 3.0 legally downloadable for free at this link: https://helpx.adobe.com/x-productkb/policy-pricing/creative-suite-2-activation-end-life.html?PID=5628473


Then head over to Quadraphonic Quad and get the Adobe Audition scripts for decoding quad recordings (there are different scripts for QS and SQ). And get the "PhaseBug" plug-in for Audition, because it's needed by these scripts.